How do I generate random number for each row in a TSQL Select?

Question

I need a different random number for each row in my table. The following seemingly obvious code uses the same random value for each row.

SELECT table_name,          


        

Answer 1

If you need to preserve your seed so that it generates the "same" random data every time, you can do the following:

1. Create a view that returns select rand()

if object_id('cr_sample_randView') is not null
begin
    drop view cr_sample_randView
end
go

create view cr_sample_randView
as
select rand() as random_number
go

2. Create a UDF that selects the value from the view.

if object_id('cr_sample_fnPerRowRand') is not null
begin
    drop function cr_sample_fnPerRowRand
end
go

create function cr_sample_fnPerRowRand()
returns float
as
begin
    declare @returnValue float
    select @returnValue = random_number from cr_sample_randView
    return @returnValue
end
go

3. Before selecting your data, seed the rand() function, and then use the UDF in your select statement.

select rand(200);   -- see the rand() function
with cte(id) as
(select row_number() over(order by object_id) from sys.all_objects)
select 
    id,
    dbo.cr_sample_fnPerRowRand()
from cte
where id <= 1000    -- limit the results to 1000 random numbers